Method of producing carbonates of the alkaline earth metals



Patented Feb. 6, i923.

UNHTED STATES PATENTv @FFHGE.

JAMES H. IVIACMAHON, OF SALTVILLE, VIRGINIA, ASSI GNOR TO THE MATHIESON ALKALI WORKS, ENG, A CORPORATION OF VIRGINIA.

METHOD PRODUCING CARBONATES OF THE ALKALINE EARTH METALS.

No Drawing.

To all whom it may concern:

Be it known that 1, JAMES H. MACMAHON, a citizen of the United States, residing at Saltville, in the county of Smyth and State of Virginia, have invented certain new and useful Improvements in Methods of Producing Carb'onates of the Alkaline Earth Metals, of which the following is a full, clear, and exact description.

This invention relates to the conversion of inexpensive and abundant compounds of the alkaline earth'metals into more valuable compounds. It more particularly relates to a method for this purpose which can be very advantageously practiced in conjunction with the ammonia soda industry.

My invention contemplates the conversion of sulphids of the alkaline earth metals into carbonates of the same metals by -first converting them into a soluble compound and then reacting upon the latter with a carbonate of ammonia which produces the desired carbonate of the metal and also a soluble compound of sulphur and ammonia. The ammonia sulphur compound can be readily converted into a more valuable product'by reacting upon the same with a hydroxid of an alkali metal to form a sulphid of the alkali metal and liberate the ammonia. The latter may be employed in the ammonia soda industry to regenerate or provide the carbonate of ammonia neces sary for use in treating further quantities of the soluble sulphids of the alkaline earth metal. fi

' More particularly 1 contemplate utilizing my invention in connection with the manufacture of barium compounds. .The mineral barytes or barite, which is chiefly barium sulphate, occurs abundantly and'is obtainable at a relatively low cost. in water and I first convert it into the soluble sulphid by calcining the same with coal dust, the product being commonly called barium black ash. The barium black ash is then'lixiviated in a well known manner and filtered to provide a clear solution of the barium sulphid, and this solution is treated with a carbonate of ammonia, preferably obtained by heating the liquor coming from It is insoluble Application filed August 20, 1920. Serial No. 404,787.

the bicarbonate filters of the ammonia soda iicient to i'orm alkali sulphid and free ammonia, (or ammonium hydroxid) to the equation:

2 na s 2NaOH Na S mince Upon heating this mixture free ammonia. is expelled, which is then returned to the ammonia soda process or utilized in other ways. In the preferred method of practising the invention the ammonia is returned to the ammonia soda process, thus acting through a cycle or series of reactions. After the ammonia has been distilled or expelled, the alkali sulphid solution may be further concentrated in open pans or pots similar to the heavy cast iron pots usually employed in completing the dehydration or finishing of caustic alkali. I find that in practice the filtrate from the sodium bicarbonate contains sodium chlorid, ammonium c lorid, ammonium bicarbonate and usually a little sodium sulfate, the latter as an impurity since most natural brines and rock salt con- ,tain gypsum. In order to utilize the ammonium bicarbonate in the manner indicated, it is best to expel the ammonium bicarbonate from this saline filtrate. It is well according recognized that on heating ammonium bicarbonate solution it is partially broken up .forming free carbon dioxid and ammonia,

trate, yields barium carbonate when passed into a solution of barium sulfid. It is immaterial that some excess carbon dioxide passes over with the ammonia since carbon dioxide also precipitates barium car:

bonate from barium sulfid solutions, forming hydrogen sulfid. In the event that fre hydrogen sulfid is formed, it is readily expelled by heating, passing the gas into a caustic alkali scrubber to form alkali sulfid. Theoretically it may be assumed that the following reactions may occur, probably simultaneously:

Practically, however, it is not necessary to take these possibillties into account since the net result 1s that desired, i. e., the precipitation of barium carbonate, and the formation of alkali sulfid and free ammonia.

The same net results can be achieved by mixing barium sulfid solution and the saline ammonium bicarbonate solution such as that coming from the bicarbonate filters of the ammonla soda process,.the resulting action from which may be conveniently represented by the equation:

(7) Bas+NH,Hoo, Baoo',+uH, s.' The precipitated barium carbonate is filtered ofl and the solution'ammonium hydro gen sulfid expelled by heating, by a current of air, by application of vacuum, or by similar processes or a combination of them, and reacting upon the evolved gas withcaustic alkali to form free ammonia and alkali'sule ,fid. It is best to remove the barium carbonate by filtration because if the mixture of finely divided barium carbonate is heated in the solution which contains lammonium chlorid, a further reaction will take place between the latter and the barium carbonate to convert the carbonate into barium chlorid, v a result not desired in this method.

When thepresence of salt which is always present in the liquor from the bicarbonate filters in the alkali sulfid is not objectionable, or when the alkali sulfid is to be used in the. form of an aqueous solution, the fil-.

trate from the precipitated barium. carbon-f he ate obtained ,as in equation (7) may treated with sufiicient caustic alkali to expel all of the ammonia, after which the solution.

will contain salt and alkali sulfid., If de-zl sired, it is obvious that the salt can be sepa rated by concentrating and filtering the crys tallized salt from the hot solution,'substari' tially in the manner in which salt is sepae rated from caustic alkali, and' alkali sulfi't permitted to crystallize by cooling the-hot filtered solution. When evaporated down to the well known commercial grade,'known as fused sodium sulfid, 60% Na s, this product when made according to the last described method contains a little salt. In other words the separation of salt and sodium sulfid can- -n6t be effected completely by known economic methods, although I find that sodium sulfid'made according to'this method is sufii ciently pure for the requirements of the industries.

The barium carbonate produced inaccordance with any of these methods is of exceptional purity andLbecause of its production as a precipitate is in a very finely divided form which is necessary for its use 1n the.

manufacture of barium peroxid, and for use as a paper filler, in paint pigments, etc. This uniform finely divided condition cannot be successfully produced by grindin The ammonia which has been liberated y these reactions may be utilized in the usual ammonia soda process, which process is so well known that a detailed description is believed to be unnecessary and further carbonates of ammonia obtained from the filter liquor thereof for use in treating additlonal qualities of barium sulfid.

' It will thus be seen that while the method of my invention is divisible in its broader aspects from the ammonia soda industry, its

' operation in conjunction with the. soda, in-

flustr-y has a very decided economic advantage inasmuch as the free ammonla whlch is liberated in the reactions occurring subsequent to the precipitation of the barium carbonate can be used in the ammonia soda process and through it, carbonates, of amprises reacting upon barium sulphid with the carbonate of ammonla in the liquor coming from the bicarbonate filters of the am.-

1rnonia soda process, to precipitate barium carbonate. j

.'2. Themethod for the commercial pro-,

duction of barium carbonate which comprises reacting upon barium sulphid with the carbonate of ammonia in the liquor coming from the bicarbonate filters of the ammonia soda-process, to precipitate barium carbonate in a solution of ammonium sul- 'phid, and recovering" the ammonia from the ammonium sulphid by reacting upon the solution with a caustic alkali to form alkali sulphid and free ammonia."

3. The method for the commercial produc tion of barium carbonate which comprises reacting upon barium sulphid with the car bonate of ammonia the liquor coming 13( from the bicarbonate filters of the ammonia ammonia soda processto obtain additional soda process to precipitate barium carbonate filter liquor for treating further barium in a solution of ammonium sulphid, recoversulphid. 10 ing: the ammonia from the ammonium sul- In Witness whereof, I hereunto subscribe phitl by reacting upon the solution with a my signature.

caustic alkali to form alkali sulphid and free ammonia, and utilizing the ammonia in the JAMES H. MACMAHON. 

